Inkjet printheads can fail for a variety of reasons. For example, air bubbles end up in an inkjet printhead or water may evaporate from aqueous ink and create a viscous plug resulting in a failure of a nozzle of the inkjet printhead. Many times, the locations of the air bubbles or viscous plug are such that they can be purged out of the printhead with a normal purge operation. However, sometimes the air bubbles or viscous plugs end up in locations where purging is ineffective.
Unpurgable air bubbles and viscous plugs do not typically happen during normal operation of the printhead. Rather, these generally occur due to a reliability failure event, such as printing with a kinked ink feed tube, with a supply valve closed, or allowing ink in an unused printhead to dry over a long period of time. Unpurgable air bubbles and/or viscous plugs may cause intensity variation, drop placement variations, or simply prevent inkjets from ejecting ink drops.
Traditional solutions have included hiding missing inkjets that are affected by the air bubbles or viscous plugs. As fresh degassed ink is used in the printhead, air bubbles eventually dissolve and/or water will diffuse into viscous plugs of ink, and the missing inkjets will work again. However, this solution only works if there are a small number of inkjets affected. If too many inkjets are affected, the printhead may be removed and simply replaced.
What is needed is an ability to recover inkjets that are affected by unpurgable air bubbles or viscous plugs without removing the printhead or hiding the affected inkjets. This may eliminate printhead replacement and reduce printer downtime.